    since you can't remove the outmost parens."
   [tree point-index]
   (let [index (mod (math/abs point-index) (count-points tree))
-        zipper (zip/seq-zip tree)]
+        zipper (seq-zip tree)]
     (if (zero? index)
       tree ;; can't remove entire tree's parens
       (let [z-found (loop [z zipper i index]

  "Returns a subtree of tree indexed by point-index in a depth first traversal."
  [tree point-index]
  (let [index (mod (math/abs point-index) (count-points tree))
        zipper (zip/seq-zip tree)]
    (loop [z zipper i index]
      (if (zero? i)
        (zip/node z)


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;; utilities

(defn seq-zip
  "Returns a zipper for nested sequences, given a root sequence"
  {:added "1.0"}
  [root]
  (zip/zipper seq?
          seq
          (fn [node children] (with-meta children (meta node)))
          root))

(defn ensure-list [thing] ;; really make-list-if-not-seq, but close enough for here
  (if (seq? thing)
